1) Field of the Invention
The field of this invention relates to pipes and more particularly to a coupling for different sections of pipe which are to be connected together in a fluid tight manner without requiring welding, soldering, or other conventional types of permanent securing techniques.
2) Description of the Prior Art
Plastic pipe and metal pipe have long been used in the conveying of fluids such as liquids and gases. These pipes include fittings with these fittings being utilized to connect together aligned different sections of pipe. These fittings must be capable of providing a fluid tight seal over a range of temperatures, pressures and a variety of exterior ambient conditions. Specifically for plastic pipe, a reliable coupling is difficult due to stress causing fatigue, stretching or failure of the plastic pipe that will result in leaking of the coupling from an inadequate seal. Couplings used in plastic pipe must be able to withstand axial stresses such as those caused by temperature induced length variations without a decrease in sealing capabilities. In addition, pipe couplings should be easily connectable by ordinary workers that don't require any special skill in order to install the coupling.
Pipe couplings are currently available in many different configurations. The typical coupling includes a body or connector portion into which an open end of a section of pipe is inserted and fixedly secured within that connector. A retaining nut is movably mounted on another section of the pipe with its open end to then be located within the confines of the connector. The retaining nut is then threaded onto the connector. Included within the connector and encircling the pipe are one or more elastic sealing rings, one or more washers, and a grip ring for longitudinally fixing in position the pipe section that has been inserted within the connector. Tightening of the retaining nut onto the connector forces this grip ring to compress radially inward to grip the wall surface of the pipe and also provide a longitudinal pressure against the sealing rings to compress such and form a fluid tight seal between the exterior wall surface of the pipe and the interior of this coupling. In the past, typical coupling designs include a grip ring that must be initially expanded radially during insertion of the pipe so as to fit around and grip the pipe. This initial radial expansion makes insertion of the pipe more difficult and creates a locking condition that prevents withdrawal of the pipe except by dissembling of the coupling even though the retaining nut has not been tightened. Also the gripping rings of the prior art have not been constructed to be readily flexible as they have a substantially thick walled surface. Flexibility is important to maximize the gripping force between the grip ring and the wall surface of the pipe.
Also, in the past, these pipe couplings have been designed to be employed only in conjunction with plastic pipe. It was not considered feasible to utilize a grip ring in conjunction with the metallic pipe prior to the present invention.